* WHAT. Heat index values up to 105 expected, up to 107 degrees closer to the Chesapeake Bay. * WHERE. In Maryland, Anne Arundel, Prince Georges, Cecil, Southeast Harford, Southern Baltimore, Calvert, Charles, and St. Marys Counties. In Virginia, King George County. * WHEN. From 1 PM to 7 PM EDT Tuesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Heat index values up to 105 expected, up to 107 degrees closer to the Chesapeake Bay. * WHERE. In Maryland, Anne Arundel, Prince Georges, Cecil, Southeast Harford, Southern Baltimore, Calvert, Charles, and St. Marys Counties. In Virginia, King George County. * WHEN. From 1 PM to 7 PM EDT Tuesday. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Flash flooding caused by excessive rainfall is possible. * WHERE. The District of Columbia, and portions of Maryland, including the following areas, Anne Arundel, Calvert, Carroll, Cecil, Central and Southeast Howard, Central and Southeast Montgomery, Charles, Northern Baltimore, Northwest Harford, Northwest Howard, Northwest Montgomery, Prince Georges, Southeast Harford, Southern Baltimore and St. Marys, and northern Virginia, including the following areas, Arlington/Falls Church/Alexandria, Central and Southeast Prince William/Manassas/Manassas Park, Eastern Loudoun, Fairfax and Northwest Prince William. * WHEN. From this afternoon through this evening. * IMPACTS. Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Flooding may occur in poor drainage and urban areas. * ADDITIONAL DETAILS. - Numerous showers and thunderstorms will move across the area this afternoon and evening. Rainfall rates of up to 2 inches per hour are possible, which may lead to scattered instances of flash flooding where the heavy rain persists the longest. - Please visit www.weather.gov/safety/flood for flood safety and preparedness information.

* WHAT. Heat index values up to 106 expected. * WHERE. The District of Columbia. In Virginia, Spotsylvania, Central and Southeast Prince William/Manassas/Manassas Park, Fairfax, and Stafford Counties, and Arlington/Falls Church/Alexandria. * WHEN. From 1 PM this afternoon to 7 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.

* WHAT. Heat index values up to 106 expected. * WHERE. In Maryland, Anne Arundel, Prince Georges, Cecil, Southeast Harford, Southern Baltimore, Calvert, Charles, and St. Marys Counties. In Virginia, King George County. * WHEN. From 1 PM this afternoon to 7 PM EDT this evening. * IMPACTS. Hot temperatures and high humidity may cause heat illnesses.